Methods for operating sensors are implemented in the art in two alternative ways. The first way corresponds to a polling method, whereby a central control unit polls every connected sensor according to a given polling period or polling frequency to receive a current sensor value and compares the received sensor value to at least one given threshold, i.e. an upper or a lower threshold. Accordingly, the central control unit has to reserve resources for performing the polling, whereby the required resources increase with the number of connected sensors. The second way refers to an interrupt driven approach, whereby each sensor comprises a logic circuit for comparing its sensor value to at least one threshold value, i.e. an upper or a lower threshold, and generates an interrupt to the central control unit, when the sensor value is above the upper threshold or below the lower threshold. In case the sensor has the two thresholds implemented, the interrupt is generated when the sensor value leaves a sensor value range lying between the upper and the lower threshold. The interrupt driven operation generally reduces the processing workload of the central control unit, because it is not continuously occupied and only has to handle the incoming interrupts. Nevertheless, the interrupt driven approach also has drawbacks. First of all, in case of frequent changes of the sensor value or the sensor value remaining for an extended time above the upper threshold or below the lower threshold, a high number of interrupts can be generated by the sensor and thereby create a significant work load for the central control unit. As specified below, the number of interrupts can be reduced, e.g. by a modification of the thresholds.
In computer systems, also referred to as IT-systems, many physical sensors can be provided and operated for monitoring sensor parameters, e.g. the temperatures, currents, voltages and/or other physical values relevant for the computer systems. The sensors are usually monitored by the IT system itself, which means that at least one CPU core of the IT-system fulfils the task of the central control unit. Accordingly, the performance of IT-systems decreases the more resources are required for monitoring the sensors. Since these IT systems can comprise a high number of sensors, the performance of the IT system can be significantly reduced because of monitoring the sensors. This problem can be overcome by monitoring the sensors based on an interrupt driven approach in combination with an adaptation of the sensor value range upon generation of an interrupt. After generation of an interrupt, a modified sensor value range is applied to the sensor, whereby the modified sensor value range covers the sensor value generating the interrupt. Accordingly, no further interrupts are generated unless the sensor value leaves the modified sensor value range. This is implemented for each sensor independently. Thereby, the central control unit is not triggered again by additional interrupts when the sensor value remains constant, i.e. outside the former sensor value range. New interrupts are only generated, when the sensor value changes and leaves the modified sensor value range. Additional interrupts, which would indicate a sensor value equal to a sensor value which already generated an interrupt, are prevented and the occupation of resources of the central control unit is reduced.
Problems can occur regarding the reliability of sensors and the detection of interrupts. Depending on the environment conditions of a sensor, the reliability can be limited or decrease with lifetime of the sensor. For example thermal conditions like high ambient temperatures have a negative impact on the reliability of sensors. In some cases interrupts may be lost, e.g. due to electric or electronic defects, so that the central control unit will not be informed about the sensor value passing the at least one threshold value. In other cases interrupts can be created although the sensor value lies within the sensor value range. Nevertheless, to achieve reliable measurement data, it is important to place sensors close to heat sinks, so that the sensors are exposed to high temperatures. Thermal conditions are crucial in IT-systems, where components of the IT-system can be damaged when exposed to high temperatures.